Re: [PATCH v4 3/7] dt-bindings: dmaengine: xilinx_dma: add optional xlnx,sg-length-width property

[Andrea Merello]

On Tue, Aug 7, 2018 at 4:56 PM, Rob Herring <robh@xxxxxxxxxx> wrote:
> On Thu, Aug 02, 2018 at 04:10:08PM +0200, Andrea Merello wrote:
>> The width of the "length register" cannot be autodetected, and it is now
>> specified with a DT property. Add DOC for it.
>>
>> Cc: Rob Herring <robh+dt@xxxxxxxxxx>
>> Cc: Mark Rutland <mark.rutland@xxxxxxx>
>> Cc: devicetree@xxxxxxxxxxxxxxx
>> Cc: Radhey Shyam Pandey <radhey.shyam.pandey@xxxxxxxxxx>
>> Signed-off-by: Andrea Merello <andrea.merello@xxxxxxxxx>
>> Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@xxxxxxxxxx>
>> ---
>> Changes in v2:
>>       - change property name
>>       - property is now optional
>>       - cc DT maintainer
>> Changes in v3:
>>       - reword
>>       - cc DT maintainerS and ML
>> Changes in v4:
>>       - specify the unit, the valid range and the default value
>> ---
>>  Documentation/devicetree/bindings/dma/xilinx/xilinx_dma.txt | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/dma/xilinx/xilinx_dma.txt b/Documentation/devicetree/bindings/dma/xilinx/xilinx_dma.txt
>> index a2b8bfaec43c..aec4a41a03ae 100644
>> --- a/Documentation/devicetree/bindings/dma/xilinx/xilinx_dma.txt
>> +++ b/Documentation/devicetree/bindings/dma/xilinx/xilinx_dma.txt
>> @@ -41,6 +41,10 @@ Optional properties:
>>  - xlnx,include-sg: Tells configured for Scatter-mode in
>>       the hardware.
>>  Optional properties for AXI DMA:
>> +- xlnx,sg-length-width: Should be set to the width in bits of the length
>> +     register as configured in h/w. Takes values {8...26}. If the property
>> +     is missing or invalid then the default value 23 is used. This is the
>> +     maximum value that is supported by all IP versions.
>
> If 23 is the max, then why is the range 8-26?

26 In the max possible value and it is supported by some HW IP flavours.
23 is the max value supported by ALL HW IP flavours